Today, various forms of imaging systems are used in the healthcare and research fields. In some cases, the imaging may be performed in vivo, i.e., within a living organism. Such imaging systems may include, for example, endoscopic imaging systems, laparoscopic imaging systems, open space imaging systems, and the like. In other cases, the imaging may be performed ex vivo, such as in the case of imaging biopsied tissue.
In general, fluorescence imaging entails capturing images of a fluorescent dye (e.g., a fluorophore) present within a subject. Such a dye may exhibit fluorescence, which is a mechanism by which a compound emits light at certain wavelengths when it is absorbs light of certain wavelengths. Often, the absorption wavelength is at a shorter wavelength than that of the emitted light during fluorescence.
In some cases, a fluorophore may exhibit multiple absorption and/or fluorescence peaks at different wavelengths. In such cases, the largest absorption and fluorescence peaks are typically selected for purposes of excitation and fluorescence imaging. This provides the greatest opportunity to detect the fluorophore within the subject undergoing imaging. While this approach may be suitable in many cases, it does so by effectively ignoring the secondary spectral peaks of the fluorophore, which may still be of use, from an image processing standpoint. Moreover, imaging of fluorophores emitting in the visible spectrum is problematic due to auto-fluorescence from endogenous molecules. Auto-fluorescence generates false-positive signals, which can be devastating if the visible fluorescence from the fluorophore is being used to resect tumors in the brain or elsewhere. In this case, otherwise healthy tissue would unnecessarily be targeted for resection. The present invention uses auto-fluorescence-free NIR signals to mask visible signals and thus improve both sensitivity and specificity of fluorescence imaging.
In the figures, reference numbers refer to the same or equivalent parts of the present invention throughout the several figures of the drawing.